The present invention relates to a control apparatus for an automatic transmission and a control method for an automatic transmission. In particular, the invention relates to a control apparatus for an automatic transmission for controlling a hydraulic pressure employed in a shift of the automatic transmission for use in an automobile, and to a control method for an automatic transmission for controlling a hydraulic pressure employed in a shift of the automatic transmission for use in an automobile.
As one kind of a control method for an automatic transmission for use in an automobile according to the prior art, there is a technique, for example, as described in Japanese application patent laid-open publication No. Hei 6-341527. In this control method, a time from a torque phase start to an inertia phase start during shifting of the automatic transmission is measured, chronological aging (an aged deterioration) of a disengagement side clutch (a disengagement side friction engagement means) is assumed by the measured time, and then an establishment value of a hydraulic pressure of the above stated disengagement side clutch in the automatic transmission is corrected.
As to the torque phase of the automatic transmission, when paying attention to the time change about an output shaft torque To of the automatic transmission, namely an output shaft torque signal (To signal, to be discussed later), the above stated torque phase indicates a period in which, during a shifting start time from a first gear ratio (a first speed) and a second gear ratio (a second speed), a gear ratio Gr, namely a gear ratio Gr signal, does not change. Instead, only the output shaft torque To signal changes.
Further, the inertia phase is a period in which, after the torque phase, the clutch, which is the friction engagement means of the automatic transmission, begins to engage and the gear ratio Gr changes.
However, as described in the Japanese application laid-open patent publication No. Hei 6-341527 mentioned above, chronological aging of a specific friction engagement means (a specific clutch) in a specific shift pattern of the automatic transmission is detected and a hydraulic pressure command value is corrected in every shift pattern, such as 1-2 shift and a 2-3 shift. With respect to a respective engagement side clutch and a respective disengagement side clutch, it is necessary to have a way to judge chronological aging (the aged deterioration).
According to the shift pattern, for example, in a case of a 4-1 shift, since all three clutches are engaged and disengaged, it is difficult to judge chronological aging separately for every clutch. As a result, a problem is caused in which a suitable hydraulic pressure correction during the chronological aging in the automatic transmission is not practiced.
Further, as another kind of a control method for an automatic transmission for use in an automobile, there is, for example, Japanese application patent laid-open publication No. Hei 8-312772. In the control method for the automatic transmission according to this second example of prior art, a first gear ratio pattern (a first shift pattern or a first speed pattern) and a second gear ratio pattern (a second shift pattern or a second speed pattern) are obtained by engaging a friction engagement means (a clutch), a hydraulic pressure correction is practiced, and then a learning and a control for the automatic transmission is attained.
With respect to a respective engagement side clutch and a respective disengagement side clutch, it is necessary to have a way in which to judge the chronological aging (the aged deterioration). However, according to the shift pattern, it is difficult to judge chronological aging separately for every clutch. As a result, a problem is caused in which a suitable hydraulic pressure correction during chronological aging in the automatic transmission is not practiced.
Namely, in the above stated control method for the automatic transmission according to this second example of the prior art, there is suggestion of employing a characteristic value of the friction engagement means (the clutch) and, further, there is no suggestion of a countermeasure for chronological aging in the automatic transmission.
An object of the present invention is to provide a control apparatus for an automatic transmission and a control method for an automatic transmission wherein, when chronological aging of a specific friction engagement means in a specific shift pattern is judged, by correcting a hydraulic pressure command value in the automatic transmission at another shift pattern to which the above stated friction engagement means contributes, even with chronological aging in some friction engagement means, at all shifts, a good shift characteristic in the automatic transmission can be obtained.
To solve the above stated problems, according to the present invention, in a control apparatus for an automatic transmission in which a shift for the automatic transmission is practiced by engaging and releasing a predetermined friction engagement means in the automatic transmission connected to an engine, during the shift for the automatic transmission, a hydraulic pressure which acts on the predetermined friction engagement means is pressure regulated and, further, the control apparatus comprises a pressure regulation command generation means enabling a change in a pressure regulation characteristic. The control apparatus for the automatic transmission comprises an operation condition recognition means for recognizing at least a shift pattern and an engine load, a chronological aging judgment means for judging a chronological aging of the predetermined friction engagement means which contributes to the shift for the automatic transmission, and a characteristic value store means for storing a characteristic value of the predetermined friction engagement means. When the friction engagement means is judged to have a chronological aging, the characteristic value stored in the characteristic value store means is changed.
According to the present invention, in a control apparatus for an automatic transmission which is connected to an engine having a predetermined friction engagement means for engaging and disengaging to practice a shift for the automatic transmission, the control apparatus for the automatic transmission comprises a hydraulic pressure regulation command generation means which, during shifting of the automatic transmission, is for regulating a hydraulic pressure which acts on the predetermined friction engagement means and for changing a hydraulic pressure regulation characteristic, an operation condition recognition means for recognizing a shift pattern and an engine load, a chronological aging judgment means for judging a chronological aging of the predetermined friction engagement means which contributes to the shift for the automatic transmission, and a characteristic value store means for storing a characteristic value of the predetermined friction engagement means.
According to the present invention, in a control method for an automatic transmission which is connected to an engine in which a shift for the automatic transmission is practiced by engaging and disengaging a predetermined friction engagement means, the control method for the automatic transmission comprises the steps of controlling an output shaft torque of the automatic transmission during shifting of the automatic transmission by regulating a hydraulic pressure which acts on the predetermined friction engagement means, recognizing a shift pattern and an engine load, judging a chronological aging of the predetermined friction engagement means which contributes to the shift for the automatic transmission, and, when the predetermined friction engagement means is judged to present chronological aging, changing a characteristic value of the predetermined friction engagement means.